1. WATER

2. Why is Water Important?
Can dissolve just about anything (including gold)!
Liquid water can carry substances around cells, organisms, ecosystems, or the planet
Allows chemical reactions to occur
Helps to shape enzymes – special proteins needed for life’s chemical reactions

3. How Unique is Water??
Water is one of only 3 naturally occurring inorganic liquids (mercury and ammonia)
Only chemical compound that exists in all 3 states—solid, liquid, and gas
Extremely large liquid range (0oC - 100oC)
Expands, becomes less dense as a solid

4. Water is a polar compound…
Shares e- unevenly
Oxygen atom in water takes on a slight negative charge, the Hydrogen atoms take on a slight positive charge

5. Water’s polarity allow it to form Hydrogen bonds
Weak bonds that form between positively charged H and negative end of another polar compound

6. In liquid water, H bonds form and break quickly
In solid ice, H bonds lock water molecules in place (making it less dense)

7. Water has ability to absorb large amounts of energy
Freezes at 0oC
Boils at 100oC

8. Hydrogen bonding accounts for
Cohesion
Adhesion

9. Water is the universal solvent:
Ionic Compounds
Other polar compounds

10. Mixtures
Homogeneous- even throughout
Heterogeneous- uneven throughout

11. Solutions
Mixtures in which one or more substances are uniformly distributed in another
Solute – substance being dissolved (ex. salt or sugar)
Solvent – substance in which the solute dissolves (ex. water)
Amount of solute dissolved = concentration

12. Other Mixtures Suspension – particles do not dissolve
“hang” or suspend in water due to movement of water molecules
Over time they settle out
Colloid – particles do not settle out over time

13. Size of Particles Solution (small) Colloid (intermediate) Suspension
(large)

14. pH scale

15. pH scale H2O will spontaneously split to form H+ and OH-
H+ and OH- will further react to form H3O+ (hydronium) and OH- (hydroxide)
In pure water, H3O+ = OH- , so water is neutral
pH scale is based on the number of H3O+ and OH- in solution

16. Acids and Bases An acid has more H3O+ while a base has more OH- Ex.
neutral acid

17. pH scale Ranges from 0 - 14 7 is neutral (water) pH < 7 = acid
pH > 7 = base
Based on a factor of 10

18. pH in an organism Most cells work best around pH 7
Too high or too low pH cause enzymes in the body to stop working
To prevent large pH swings, organisms use buffers